System and method for coexistence of grant-free and grant-based uplink traffic

ABSTRACT

Systems and methods of scheduling grant-based traffic and mapping resources for grant-free traffic are provided. Grant-based traffic is scheduled in a first frequency partition, and grant-free traffic is mapped in a second frequency partition. In a first option, grant-based traffic is also scheduled in part of the first partition, but in a limited manner that ensures a given device&#39;s transmission and retransmissions do not all experience interference with the grant-based traffic. In another option, some grant-free traffic is mapped to part of the second partition and is spread in frequency across the second partition.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/142,638 filed Apr. 29, 2016, which is incorporated by reference inits entirety.

FIELD

The present application relates a system and method for coexistence ofgrant-free uplink traffic with grant-based uplink traffic.

BACKGROUND

In many wireless networks, such as long-term evolution (LTE) networks,the selection of shared data channels for uplink isscheduling/grant-based, and the scheduling and grant mechanisms arecontrolled by a base station (BS) in the network. A user equipment (UE)sends an uplink scheduling request to the BS. When the BS receives thescheduling request, the BS sends an uplink grant to the UE indicatingits dedicated uplink resource allocation. The UE then transmits data onthe granted resource. This is a specific example of grant-based uplinktraffic.

In contrast, for grant-free traffic, independent of any schedulingrequest, a UE may be mapped to resources for grant-free transmission.The resources are not dedicated to a UE, and there can be multiple UEsmapped to the same resource. In grant-free transmission, a UE does notrely on a dynamic scheduling request and grant mechanism to transmitdata. A given UE that has no data to transmit will not transmit usingthe mapped resources.

SUMMARY

A broad aspect of the invention provides a method of schedulinggrant-based traffic and mapping resources for grant-free traffic. Themethod includes scheduling uplink grant-based traffic in a firstfrequency partition. A plurality of UEs are mapped for uplink grant-freetransmission to time-frequency regions of a second frequency partitionthat does not overlap with the first frequency partition by mapping eachUE to a respective plurality of time-frequency regions. Uplinkgrant-based traffic is scheduled in at least one portion of the secondfrequency partition, such that for at least one UE of said plurality ofUEs configured for a plurality of uplink grant-free transmissions thatincludes an initial grant-free transmission and at least one grant-freeretransmission using time-frequency regions indicated by said mapping,at least one of the uplink grant-free transmissions overlaps with the atleast one portion of the second frequency partition, and at least one ofthe uplink grant-free transmissions does not overlap with the at leastone portion of the second frequency partition.

Optionally, the scheduling and mapping are subject to a constraint thatfor any UE of said plurality of UEs that transmits an initialtransmission and a fixed number of retransmissions, at most apredetermined number of time-frequency regions used for the UE's initialtransmission and retransmissions overlap with the at least one portionof the second frequency partition.

Optionally, differing UEs each transmit differing numbers ofretransmissions. A different constraint can be applied depending on thenumber of retransmissions.

Optionally, scheduling uplink grant-based traffic comprises schedulingenhanced mobile broadband (eMBB) traffic; and mapping the plurality ofUEs for uplink grant-free transmission comprises mapping UEs forultra-reliable low latency (URLL) traffic.

Optionally, mapping a plurality of UEs for uplink grant-freetransmission to time-frequency regions of a second frequency partitionthat does not overlap with the first frequency partition is done suchthat no two UEs can overlap for both an initial transmission and allretransmissions.

Another broad aspect of the invention provides another method ofscheduling grant-based traffic and mapping resources for grant-freetraffic. The method includes scheduling uplink grant-based traffic in afirst frequency partition. A UE is mapped for an initial uplinkgrant-free transmission to a time-frequency region of a second frequencypartition that does not overlap with the first frequency partition. TheUE is also mapped for an uplink grant-free retransmission in at leastone portion of the first frequency partition, such that mapped resourcefor the retransmission is spread across the first frequency partition. Afirst transmission time unit (TTU) duration is used for grant-basedtraffic in the first frequency partition, and a second TTU duration isused for grant-free transmission in the second frequency partition, andfor grant-free transmission in the at least one portion of the secondfrequency partition, the second TTU duration being shorter than thefirst TTU duration.

Another broad aspect of the invention provides a network elementcomprising a scheduler and a mapper. The scheduler is for schedulinguplink grant-based traffic in a first frequency partition. The mapper isfor mapping a plurality of UEs for uplink grant-free transmission totime-frequency regions of a second frequency partition that does notoverlap with the first frequency partition by mapping each UE to arespective plurality of time-frequency regions. The scheduler is furtherconfigured to schedule uplink grant-based traffic in at least oneportion of the second frequency partition. The scheduling is such thatfor at least one UE of said plurality of UEs configured for a pluralityof uplink grant-free transmissions that includes an initial grant-freetransmission and at least one grant-free retransmission usingtime-frequency regions indicated by said mapping, at least one of theuplink grant-free transmissions overlaps with the at least one portionof the second frequency partition, and at least one of the uplinkgrant-free transmissions does not overlap with the at least one portionof the second frequency partition.

Another broad aspect of the invention provides a network elementcomprising a scheduler and a mapper. The scheduler is for schedulinguplink grant-based traffic in a first frequency partition. The mappermaps a UE for an initial uplink grant-free transmission to atime-frequency region of a second frequency partition that does notoverlap with the first frequency partition. The mapper maps the UE foran uplink grant-free retransmission in at least one portion of the firstfrequency partition, such that the at least one portion is spread acrossthe first frequency partition. A first TTU duration is used forgrant-based traffic in the first frequency partition, and a second TTUduration is used for grant-free transmission in the second frequencypartition, and for grant-free transmission in the at least one portionof the second frequency partition, the second TTU duration being shorterthan the first TTU duration.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a network supporting grant-based UEs andgrant-free UEs;

FIG. 2 is an example set of CTU definitions;

FIG. 3A is a first example of coexistence of traffic for grant-based UEswith traffic for grant-free UEs using different numerologies;

FIG. 3B is a first example of coexistence of traffic for grant-based UEswith traffic for grant-free UEs using a common numerology;

FIG. 4 is another example of coexistence of traffic for grant-based UEswith traffic for grant-free UEs;

FIG. 5 is an example of mapping grant-free UEs that transmit an initialtransmission and one retransmission;

FIG. 6 is example of a generic division of a partition for grant-freetransmission into segments, TTUs, and regions;

FIGS. 7A, 7B and 7C are three examples of mapping grant-free UEs thattransmit an initial transmission and one retransmission;

FIG. 8 is an example of mapping grant-free UEs that transmit an initialtransmission and two retransmissions;

FIG. 9 is an example mapping grant-free UEs that transmit an initialtransmission and one retransmission together with UEs that transmit aninitial transmission and two retransmissions;

FIG. 10 is a flowchart of a first method of scheduling uplinkgrant-based traffic and mapping uplink grant-free traffic;

FIG. 11 is a block diagram of a first network element that schedulesuplink grant-based traffic and maps uplink grant-free traffic;

FIG. 12 is an example of mapping grant-free UEs to transmit an initialretransmission in a partition for grant-free traffic, and aretransmission using resources within a partition for grant-basedtraffic. uplink grant-based traffic and mapping uplink grant-freetraffic;

FIG. 13 is a flowchart of a second method of scheduling uplinkgrant-based traffic and mapping uplink grant-free traffic; and

FIG. 14 is a block diagram of a second network element that schedulesuplink grant-based traffic and maps uplink grant-free traffic.

DETAILED DESCRIPTION

Generally, embodiments of the present disclosure provide a method andsystem for grant-based traffic to coexist with grant-free traffic foruplink transmissions. For simplicity and clarity of illustration,reference numerals may be repeated among the figures to indicatecorresponding or analogous elements. Numerous details are set forth toprovide an understanding of the examples described herein. The examplesmay be practiced without these details. In other instances, well-knownmethods, procedures, and components are not described in detail to avoidobscuring the examples described. The description is not to beconsidered as limited to the scope of the examples described herein.

For the purpose of this description, a grant-free UE is a UE that isconfigured to transmit grant-free traffic. The UE may also have othercapabilities including transmission of grant-based traffic. Grant-freetransmission means that a UE does not rely on a dynamic schedulingrequest and grant mechanism to transmit data. The transmission resourcesand formats (e.g. coding and modulation schemes) are pre-configured orsemi-statically configured. Similarly, a grant-based UE is a UE that isconfigured to transmit grant-based traffic, but such a UE may also haveother capabilities including transmission of grant-free traffic.

Referring to FIG. 1 , a schematic diagram of a network too is shown. Abase station (BS) 102 provides uplink and downlink communication withthe network too for a plurality of user equipment (UEs) 104-118 within acoverage area 120 of the BS 102. In a specific example, UEs 104-110 areUEs that grant-free UEs, and UEs 112-118 are UEs grant-free UEs. In amore specific example, the UEs 104-110 employ OFDMA to transmit enhancedmobile broadband (eMBB) traffic. UEs 112-118 may, for example, transmittraffic which requires ultra reliability and low latency. UEs 112-118may use grant-free OFDMA or other non-orthogonal access schemes such assparse code multiple access (SCMA). The BS 102 may, for example, be anaccess point. FIG. 1 shows one BS 102 and eight UEs 104-118 forillustrative purposes, however a network too may include more than oneBS 102 and the coverage area 120 of the BS 102 may include more or fewerthan eight UEs 104-118 in communication with the BS 102.

In some embodiments, the BS 102 implements a grant-free uplinktransmission scheme in which contention transmission unit (CTU) accessregions are defined. Each CTU access region may include a number ofCTUs. A CTU is a basic resource, predefined by the network too, forcontention based transmissions. Each CTU may be a combination of time,frequency, code-domain, and/or pilot sequence elements. Code-domainelements may be, for example, CDMA (code division multiple access)codes, LDS (low-density signature) signatures, SCMA codebooks, and thelike. These possible code-domain elements are referred to generically as“signatures” hereinafter. Multiple UEs may contend for the same CTU. Thesize of a CTU may be preset by the network too and may take into accountan expected number of UEs served and their payload, the amount ofdesired padding, and/or modulation coding scheme (MCS) levels. Thegrant-free uplink transmission scheme may be defined by the BS 102, orit may be preconfigured, or configured semi-statically.

Sparse code multiple access (SCMA) is a non-orthogonal waveform withnear optimal spectral efficiency that utilizes the shaping gain ofmulti-dimensional constellations. The utilization of non-orthogonalwaveforms in SCMA enables the creation of a multiple-user multipleaccess scheme in which sparse codewords of multiple layers or UEs areoverlaid in code and power domains and carried over sharedtime-frequency resources. The system is overloaded if the number ofoverlaid layers is more than the length of multiplexed codewords.Overloading is achievable with moderate complexity of detection due tothe sparsity of SCMA codewords. In SCMA, coded bits are directly mappedto sparse codewords selected from layer-specific SCMA codebooks. Due tothese benefits, SCMA is a technology suitable for supporting massiveconnectivity. Furthermore, a blind multi-user reception technique usingMessage Passing Algorithm (MPA) decoding can be applied to detect UEs'activities and the information carried by them simultaneously. With suchblind detection capability, grant-free multiple access can be supported.A detailed description of SCMA schemes can be found in U.S. patentapplication Ser. No. 13/919,918 filed Jun. 17, 2013, entitled System andMethod for Designing and Using Multidimensional Constellations, whichapplication is incorporated herein by reference. A detailed descriptionof an MPA receiver can be found in U.S. patent application Ser. No.14/212,583 filed Mar. 14, 2014, entitled Low Complexity Receiver andMethod for Low Density Signature Modulation, which application is herebyincorporated herein by reference.

Referring now to FIG. 2 , shown is an example of resource definitionwithin the grant-free band. In this example, a time frequency resourceis divided into four regions 150, 152, 154, 156. Each region occupiesfour resource blocks. The resource blocks are only shown for region 150as RB1, RB2, RB3, RB4. In addition, for each region, there can be up tosix layers. The layering is only shown for region 154 with the sixlayers indicated at 158. Within each layer, a respective codebook isused, and in addition, a set of different pilot sequences 160 are usedto separate multiple UEs that use the same codebook. Thus, for example,in each layer of the set of layers 158, up to six different UEs cantransmit using different pilot sequences. In the example of FIG. 2 ,there are 36 unique combinations per region. If only 36 UEs are everassigned to a given region, and each is assigned a unique CTU, thenthere will be no collision, a collision occurring if two or more UEstransmit with the same CTU. However, if there are a larger number of UEsthat need to be able to be mapped to each region, then there will be thepossibility of a collision. It is noted that a pilot sequence/signaturecorrelator is used in the receiver to detect each signal.

In some embodiments, the grant-free uplink transmission scheme mayassign a unique identifying CTU index I_(CTU), to each CTU in regions150-156. Referring now to FIGS. 1 and 2 together, UEs 112-118 determinewhich CTU to transmit on based on mapping rules for mapping each UE112-118 to an appropriate CTU index. The mapping rules may be defined ina mapping scheme. The mapping scheme may be determined by the BS 102, inwhich case the mapping scheme is sent to the UEs 112-118 utilizing, forexample, high-level signaling from the BS 102 when the UEs 112-118connect to the BS 102. Alternatively, the mapping scheme may bepredefined, in which case the mapping scheme is known at the UEs 112-118prior to the UEs 112-118 connecting to the BS 102.

Utilizing a mapping scheme enables a UE to automatically transmit dataon CTUs as soon as it enters the coverage area 120 of a BS 102, withoutscheduling signaling between the BS 102 and the UE. The mapping rulesmay be based on, for example, a UE's dedicated connection signature(DCS), its DCS index assigned by a BS, the total number of CTUs, and/orother parameters such as subframe number.

In a grant-free uplink transmission scheme, in the event of a collisiondue to multiple UEs simultaneously accessing the same CTU, the BS 102 isunable to estimate the individual channels of the UEs accessing the sameCTU and, therefore, cannot decode each UE's transmission information.For example, assume two UEs (UE 112 and 116) are mapped to the same CTUand their channels are h₁ and h₂. If both UEs transmit simultaneously,the BS 102 can only estimate a channel of quality of h₁+h₂ for both UEs112 and 116, and the transmitted information will not be decodedcorrectly. However, the BS 102 can implicitly determine which UEs thetransmission came from based on the default mapping rules, for exampleby resolving the headers of each of the transmissions, even though theBS 102 is unable to explicitly determine which UEs were transmitting.

Referring to FIG. 3A, shown is a first example of co-existence ofgrant-free and grant-based traffic, for example URLL and eMBB traffic. Asystem bandwidth is divided into two frequency partitions 200, 202. Inthe example of FIG. 3A, the two partitions 200, 202 are in respectivesub-bands 201, 203 having different sub-carrier spacings. The firstfrequency partition 200 operates with a numerology having a 60 KHzsub-carry spacing, whereas the second frequency partition 202 operateswith a numerology having a 15 KHz sub-carrier spacing. In the firstfrequency partition 200, shown are four TTUs 205, 207, 209, 211 eachhaving a 0.125 ms TTU duration. For the second frequency partition 202,shown is a single TTU 213 having a 0.5 ms TTU duration. The shorter TTUduration used in the first frequency partition is suitable forgrant-free traffic requiring low latency. In some embodiments, astructure similar to that of FIG. 2 is employed within frequencypartition 200. Within TTUs 205, 207, 209, 211, shown are respectiveportions 206, 208, 210, 212 within frequency partition 200 that areavailable for grant-free traffic. Frequency partition 202 is availablefor transmitting regular scheduled grant-based traffic. In addition,portions of frequency partition 200 are also available for use intransmitting a part of regular scheduled grant-based traffic. In theillustrated example, this includes portions 214, 216 within thegrant-free band. It is noted that these grant-based portions 214, 216overlay the resources available for grant-free traffic. In this example,a different numerology is used for grant-free traffic, and some of thecapacity allocated to that numerology is also assigned for grant-basedtraffic. Because successful detection and reliability is important forgrant-free transmission, scheduling of grant-based traffic in theoverlay portions within the grant-free band is coordinated with theallocation of the grant-free resources to grant-free traffic, to avoidor mitigate the effect of collisions between the grant-based traffic andthe grant-free traffic.

Referring to FIG. 3B, shown is a second example of co-existence ofgrant-free and grant-based traffic. The example of FIG. 3B is largelysimilar to FIG. 3A, but instead of having two frequency partitions 200,202 in respective sub-bands 201, 203 with respective numerologies, shownare frequency partitions 200, 202 within a single band 220 with a 15 kHzsub-carrier spacing. Unlike the FIG. 3A example, in the FIG. 3B example,the grant-free partition 200 and grant-based partition 201 employ thesame numerology, however their TTU durations can be different. Forexample, grant-free low latency UEs may use a TTU with fewer symbolscompared to grant-based traffic. The examples that follow assume thatdiffering numerologies are used for grant-free and grant-based (i.e. theexample of FIG. 3A), but more generally, any of the approaches describedbelow can also be applied to systems in which a single numerology isused for both traffic types as per the example of FIG. 3B.

Grant-free UEs are configured to transmit an initial grant-freetransmission and at least one grant-free retransmission associated withthe initial grant-free transmission. There may be a predefined number ofretransmissions. For example, a UE can be configured to transmit aninitial transmission and one retransmission. Note that theretransmission is made irrespective of whether or not the initialtransmission was successfully received and decoded. This method ofretransmission mitigates the latency of waiting for an acknowledgement(ACK) or a negative acknowledgement (NACK) prior to retransmission,which may be unacceptable for some grant-free traffic, such as URLLtraffic. In some embodiments, one or more configurations are assignablefor a given UE in terms of the number of retransmissions the UE isexpected to make for each new transmission. This may be updated, forexample by long term adaptation.

A partition for grant-free traffic is segmented into different regionsto which grant-free UEs may be mapped. In the example of FIG. 3A,partition 200 is segmented into four TTUs 206, 208, 220, 212. UE mappingto the regions is performed, taking into account the number of regionsper TTU, and the number of UEs. Co-existence of grant-free traffic withgrant-based traffic is designed such that for each grant-free UE, thegrant-free traffic has at least one transmission that does not collidewith grant-based traffic. In some embodiments, the number of allowablecollisions is a configurable parameter, and this may be set dependingupon a number of UEs mapped to a region, the UEs' retransmission policy,and how many regions exist per TTU.

A specific example will now be described with a reference FIG. 4 . Here,the basic structure is the same as that of FIG. 3A, and the samereference numerals have been used to describe the TTUs for the frequencypartition 200 and the frequency partition 202. Each grant-free TTU isdivided into three regions. For example, TTU 211 is divided into region240, 242 and 244. There are a total of 12 regions within TTUs 205, 207,209, 211. In addition, grant-based traffic is scheduled in thegrant-free partition 202 in overlay portions 214, 216.

In the illustrated example, the grant-based scheduling interval used toschedule traffic within the grant-free partition is aligned with aregular 15 KHz TTU scheduling. This is because the grant-based trafficscheduled within the shorter grant-free TTUs is not constrained in thesame manner as grant-free traffic, and as such the grant-based trafficcan be scheduled together with the normal grant-based traffic anddecoded at the end of a TTU, for example at the end of TTU 213 in FIG.3A.

Grant-free UEs are mapped to specific regions for UL grant-freetransmission. In some embodiments, a grant-free UE is configured to usedifferent regions for an initial transmission compared to associatedretransmissions. For example, referring again to FIG. 4 , a UE thatmakes an initial transmission in region 246 may be configured to make aretransmission in region 248. This allows for increased diversitybetween the initial transmission and the retransmission. This can alsobe used to avoid resource overlap for multiple grant-free UEs for bothinitial transmissions and retransmissions. Due to a limited number ofregions, or a small bandwidth, a unique grouping for successivetransmissions may not always be possible. In some embodiments,grant-free UEs are configured to perform CTU hopping to lower thechances of collision. By definition, a different CTU is used for each ofan initial transmissions and retransmission, since different TTUs, andhence different times are used. With CTU hopping, some other aspect ofthe CTU is also different as between the initial transmission and theretransmission. In other words, the code, pilot, frequency combinationused for the initial transmission is different than that used for theretransmission. More specifically, in addition to using differentregions for an initial transmission and a retransmission, a UE may usedifferent CTUs for the two transmissions. The mapping of UEs to a regionmay be semi-static based on long term adaptation.

FIG. 5 shows an example in which a grant-free partition 300 is dividedinto four segments 302, 304, 306, 308 within each of four TTUs 310, 312,314, 316. In the illustrated example, during TTU 310, this segmentationdefines four regions 320, 322, 324, 326. Each region supports up to fourUEs in this example. A list of four numbers depicted for each regionrepresents a set of four UEs mapped to that region. A UE being mapped toa given set of regions will make grant-free transmissions using theregions to which it is mapped in a given TTU if it has data to send.However, the UE may or may not have a transmission to make in a givenregion to which it is mapped. In the illustrated example, during TTU310, UEs 1, 2, 3, 4 are mapped to segment 320; UEs 5, 6, 7, 8 are mappedto region 322; UEs 9, 10, 11, 12 are mapped to region 324; and UEs 13,14, 15, 16 are mapped to region 326. From one TTU to the next, themapping changes. Thus, during TTU 312, UEs 1, 5, 9, 13 are mapped toregion 328; UEs 2, 6, 10, 14 are mapped to region 330; UEs 3, 7, 11, 15are mapped to region 332; and UEs 4, 8, 12, 16 are mapped to region 334.Note that the entire pattern repeats for TTUs 314, 316. In this exampleit is assumed that each UE makes an initial transmission and a singleretransmission. In this example, it can be seen that regions 320 and 328can be used by UE1 for UE1's initial transmission and retransmission.The mapping is such that there are no other UEs that are in commonbetween both regions 320, 328. Thus, in this particular example, theprobability of collision between the same group of UEs in both theinitial transmission and retransmission is reduced compared to asituation where the group of UEs use the same resources for initialtransmissions and retransmissions.

In addition, it can be seen that grant-based traffic is scheduled inregions 320, 336. It can be seen that there is a potential collisionbetween the traffic of grant-based UEs and the traffic of grant-free UEs1, 2, 3, 4 in region 320. Similarly, there is a potential for collisionbetween the traffic of grant-based traffic UEs and the traffic ofgrant-free UEs 9, 10, 11, 12 in region 336. It can be seen that thegroup of grant-free UEs experiencing a potential collision differsbetween the two grant-based regions. Thus, potential collisions withgrant-based transmissions are distributed over many UEs, and eachgrant-free UE has grant-free resources available that do not collidewith grant-based transmissions.

In the example of FIG. 5 , each grant-free UE experiences a potentialcollision with grant-based traffic a maximum of one time during itsinitial transmission. More generally, in some embodiments, a definedmaximum number of collisions with grant-based traffic is a configurableparameter. By performing an appropriate mapping of UEs to regions and anappropriate definition of the grant-based regions, rules for the maximumnumber of collisions can be satisfied. For example, a rule may be thatas between a UE's initial transmission and its retransmissions, amaximum number K of collisions with grant-based traffic are allowed,where K is a configurable parameter. In the example of FIG. 5 , theparameter K is set to one.

In the example of FIG. 5 , each region supports four codebook layers,and there are four UEs mapped to be able to transmit on those layers,assuming each UE transmits on one layer. More generally, there may be alarger, in some cases much larger, number of UEs mapped to a givenregion than there are layers. For example, region 320 may have sixlayers, and may have 36 UEs mapped to that region, as described by wayof example previously with reference to FIG. 2 . In that case, somedifferent UE's traffic can be separated by using different codebookand/or pilot sequence. However, it may still be the case that there aremore UEs mapped to a region than there are unique combinations oflayers, pilot sequences and codebooks. In this case, there is thepotential for collision if multiple UEs that are transmitting on theidentical resource transmit at the same time. In some embodiments, UEsare configured to employ CTU hopping to lower the chances of collisionwith the same UE during both an initial transmission and aretransmission.

For example, referring again to FIG. 5 , the frequency segment 302 forCTU for transmission for UE2 for region 320 during TTU 310 is differentfrom the frequency segment 304 of the CTU for UE2 for region 330 duringTTU 312. The codebook and/or pilot sequence may also be changed asbetween the initial transmission and the retransmission. This reducesthe likelihood that UE2 and another UE transmit using the same first CTUfor both region 320, and using the same second CTU for region 330.

In some embodiments, each UE uses a fixed MCS for initial transmissionsand retransmissions. In other embodiments, the UE is configured tochange the MCS between transmissions. For example, a retransmission mayuse a lower MCS for more robustness.

In some embodiments, different MCSs may be transmitted over the sameregion by different UEs. Alternatively, in some embodiments, differentdivisions are defined for different MCSs.

Referring now to FIG. 6 , shown is a more general example of grant-freeUE transmission, in co-existence with grant-based traffic. A grant-freepartition 400 is divided into M segments 402, 404, 406, . . . , 408. Foreach segment, there is a respective region in each TTU 410, 412, 414, .. . , 416. For example, shown are regions 409, 411, 413, . . . , 415 insegment 402 during TTUs 410, 412, 414, . . . , 416. Each region cansupport up to K layers, for a total of MK independent layers that can besupported without collision during each TTU. Equivalently, each regioncan support MK UEs without collision if each UE transmits on one layeronly. However, in some implementations, a UE may be configured totransmit on multiple layers in a region. The mapping of UEs insuccessive TTUs can be obtained by a simple interleaving, as per theexample of FIG. 5 , for example, with the objective of having minimaloverlap between groupings from one TTU to the next. In the illustratedexample, UEs 1, 2, . . . , K are mapped to region 409. UEs K+1, K+2, . .. , 2K are mapped to region 417, . . . , and UEs MK−K+1, . . . , MK aremapped to region 419. An interleaved mapping is used for TTU 212 thatavoids overlap in the groups. For example, referring again to FIG. 5 ,it can be seen that the mapping between TTUs 310, 312 is performed suchthat for each pair of groups of UEs assigned to a given pair of regions,one in TTU 310, one in TTU 312, there is only one UE common to bothgroups. Choosing an appropriate pattern assists in defining appropriateregions for assigning to grant-based traffic opportunities.

In some embodiments, grant-based scheduling is based on the worst-casescenario in which it is assumed that all K layers of each grant-freeregion are used and grant-based UEs may adjust transmit powerpre-emptively to keep the interference to grant-free UEs under control.

In the example of FIG. 6 , three different use cases will be described.In the first example, described below with reference to FIGS. 7A, 7B,7C, all UEs retransmit only once. In a second example described belowwith reference to FIG. 8 , all UEs retransmit twice. In a third exampledescribed below with reference to FIG. 9 , a general scenario isdescribed in which some UEs retransmit once and some UEs retransmittwice. Recall for these figure descriptions that M is the number ofregions that the band is divided into and K is the number of layerssupported by each region. In all of these examples, the followingapplies:

For M<K, unique grouping in successive TTU is not possible

At least, initial transmission and retransmissions for each of twoUEs/Layers, if made, will collide

For M≥K, unique grouping in successive TTU is possible

-   For M≤K, grant-based UEs can be assigned at least one region every    second TTU-   Assigned regions may change to avoid repeated collisions between    transmissions of the same group of UEs-   For M>K, grant-based UEs can be assigned in at least one region    every TTU

EXAMPLE 1 All UEs Retransmit Only Once

In the example of FIG. 7A, M=3 and K=4. Because M is less than K, aunique grouping in successive TTUs is not possible. Thus, for example,UEs 1 and 2 are in common between the groups of UEs that are mapped toregions 500, 502. However, in the example of FIG. 7A, grant-basedtraffic is mapped to regions 504, 506, and there is no grant-free UEthat is mapped to both of these two regions. Thus, in the example ofFIG. 7A, each UE experiences a potential collision with grant-basedtraffic at most once. Some of the UEs have an increased probability ofcollision with other grant-free UEs.

In the example of FIG. 7B, M=4 and K=4. This is equivalent to theexample of FIG. 5 described previously. In this case, a unique groupingin successive TTUs is possible.

In the example of FIG. 7C, M=5 and K=4. In this case, there again can bea unique grouping in successive TTUs. In addition, a grant-based regioncan be assigned to at least one region in every TTU. In the illustratedexample, there are four TTUs, and there are four assigned grant-basedregions 520, 522, 524, 526. Each UE experiences potential collision withgrant-based traffic at most for one transmission as between an initialtransmission and a single associated retransmission.

EXAMPLE 2 All UEs Retransmit Twice

In the example of FIG. 8 , each UE makes two retransmissions afterinitial transmission. For example, a UE may make an initial transmissionduring TTU 600 and retransmissions during TTUs 602, 604. However,depending on when the UE has a packet to transmit, the initialtransmission could alternatively be made during TTU 602 withretransmissions during 604, 606. A grant-free UE will typically attemptto minimize latency by making the initial transmission during the firstavailable TTU after the packet is available to transmit. In the exampleof FIG. 8 , M=4 and K=4 and as such unique groupings between successiveretransmissions are possible. Thus, for the regions 610, 612, 614 towhich grant-free UE1 is mapped, there is no other UE that shares morethan one of these three regions. In the example of FIG. 8 , the rule forgrant-based assignment is that at most one transmission of a given UE(between its initial transmission and two retransmissions) can besubject to a potential collision with grant-based traffic. With thatconstraint, a grant-based assignment can be made in one region of thefirst three TTUs, and one region of the second three TTUs.

EXAMPLE 3 General Scenario—Some UEs Transmit Once and Other UEs TransmitTwice

Referring now to FIG. 9 , shown is an example in which some UEsretransmit once and some retransmit twice. This can be generalized to asituation where there are sets of UEs that each transmits a respectivenumber of retransmissions. In this example, after a given UE's packetarrives, it is transmitted in the next available TTU. However, othervariations are possible. For example, in a time division dupleximplementation, a UE may need to wait a certain amount of time before anuplink slot can be used. Shown are example transmissions for six TTUs700, 702, 704, 706, 708, 710. In this case, there are five segments 712,714, 716, 718, 720. UEs 1, 9, 13 are configured to retransmit once andUEs 7, 8, 6, 20 are configured to re-transmit twice. Initialtransmissions are shown as a UE number with a circle around it; firstretransmissions are shown with a UE number with a square around it;finally, second retransmissions are shown with a UE number with adiamond around it text. Where a region contains a number that is not ina circle, not in a square, and not in a diamond, this means that that UEhad the opportunity to make a grant-free transmission but did not makeone. For UE 1, shown is an initial transmission in region 730 and aretransmission in region 732. Another initial transmission is performedfor UE 1 in region 734 and a retransmission in region 736. For UE 9,shown is an initial transmission in region 730 and a retransmission inregion 746. For UE 13, shown is an initial transmission in region 748and a retransmission in region 736.

Recall that UEs 7, 8, 6, 20 perform two retransmissions. Thus, aninitial transmission is shown for UE 7 in region 742 withretransmissions in regions 754 and 738. An initial transmission for UE 8is shown in region 752 with retransmissions in regions 732, 738. Aninitial transmission for UE 6 is shown in region 738 withretransmissions in regions 740, 750. For UE 20, an initial transmissionis shown in region 756 with retransmissions in regions 758, 750. In thisexample, some UEs are configured for a single retransmission, and otherUEs are configured for two retransmissions. In this example, grant-basedtransmissions take place in regions 760, 754, 758. With the mappingillustrated, each UE experiences a potential collision with grant-basedtraffic at most once for its initial transmission and any of theretransmissions of the same packet. In addition, because M=5 and K=4,there is a unique grouping for successive retransmissions.

Referring now to FIG. 10 , shown is a flowchart of a general method ofscheduling uplink grant-based traffic and mapping resources forgrant-free transmission. The methods described above are specificexample implementations of this method. In block 800, uplink grant-basedtraffic is scheduled in a first frequency partition. In block 802, UEsare mapped for uplink grant-free transmission to time-frequency regionsof a second frequency partition that does not overlap with the firstfrequency partition. This involves mapping each UE to a respectiveplurality of time-frequency regions. In block 804, uplink grant-basedtraffic is scheduled in at least one portion of the second frequencypartition. At least one of the UEs is configured for a plurality ofuplink grant-free transmissions that includes an initial grant-freetransmission and at least one grant-free retransmission usingtime-frequency regions indicated by said mapping. The mapping and thescheduling are such that at least one of the uplink grant-freetransmissions overlaps with the at least one portion of the secondfrequency partition, and at least one of the uplink grant-freetransmissions does not overlap with the at least one portion of thesecond frequency partition.

FIG. 11 is a block diagram of a network element that schedules uplinkgrant-based traffic and maps resources for grant-free transmission. Thenetwork element includes an SOMR (Scheduler with Overlap with MappedResources) 1108 and a mapper 1110. The SOMR 1108 and the mapper togetherperform scheduling and mapping, using the method of FIG. 10 , forexample, or one of the other methods described above. The networkelement may, for example, be a base station, in which case othercomponents such as antennas 1100, a transmit chain 1104 and a receivechain 1106, and network connections 1102 are present. In a specificimplementation, the network element of FIG. 11 may include a processorand memory containing instructions that implement the mapper andscheduler.

In another embodiment, grant-free transmissions are performed usingresources that overlap with those allocated for grant-based traffic.Grant-free transmissions transmitted in the overlapping resources may,for example, use a lower code rate compared to grant-free transmissionstransmitted on resources dedicated to grant-free traffic, and may bespread in frequency over a large grant-based frequency space. An exampleis shown in FIG. 12 where a frequency band allocated to a numerologywith a 15 KHz sub-carrier spacing is divided into a first partition 1002that is dedicated to grant-free transmissions, and a second partition1004 that is used for scheduled grant-based transmissions. A relativelyhigh rate transmission is depicted at 1006 as an initial grant-freetransmission for a grant-free UE. A retransmission is indicated at 1008using a lower rate code. The retransmission 1008 uses a time frequencyresource that is overlaid over the second partition 1008. In addition,the time frequency resource used for retransmission 1008 is spread infrequency over the second partition 1004. In the example of FIG. 10 , agrant-based TTU is shown at 1010, and a grant-free TTU is indicated at1012. The initial transmission 1006 is immediately followed by theretransmission 1008 in the following grant-free TTU for low latency forthe grant-free transmissions.

In a specific example, the re-transmission uses a lower code rate, hencethere is a larger number coded bits to be transmitted for there-transmission. These can be spread over the grant-based partitionband, which may be much wider than grant-free partition. This providesrobustness against possible collision with grant-based traffic. Here,spreading over wider band also exploits frequency diversity. Spreadingover a wider band also exploits frequency diversity. As an example, thegrant-based partition is 40 resource blocks wide, with each resourceblock having 12 resource elements, for a total of 40*12=480 resourceelements (REs) in each OFDM symbol. If there is a grant-freetransmission with 24 bits to transmit that uses ¼ code rate, there are96 coded bits. With QPSK, this corresponds to 48 symbols which aremapped to 48 resource elements out of the 480 resource elements of anOFDM symbol in the grant-based partition. These 48 symbols can be spreadacross this partition, for example by transmitting one symbol on every10^(th) resource element.

FIG. 14 is a block diagram of a network element that schedules uplinkgrant-based traffic and maps resources for grant-free transmission. Thenetwork element includes a scheduler 1308 and an MOSR (Mapper thatOverlaps with Scheduled Resources) 1310. The scheduler 1308 and the MOSR1310 together perform scheduling and mapping, using the method of FIG.13 . The network element may, for example, be a base station, in whichcase other components such as antennas 1100, a transmit chain 1104 and areceive chain 1106, and network connections 1102 are present. In aspecific implementation, the network element of FIG. 14 may include aprocessor and memory containing instructions that implement the mapperand scheduler.

In the preceding description, for purposes of explanation, numerousdetails are set forth in order to provide a thorough understanding ofthe embodiments. However, it will be apparent to one skilled in the artthat these specific details are not required. In other instances,well-known electrical structures and circuits are shown in block diagramform in order not to obscure the understanding. For example, specificdetails are not provided as to whether the embodiments described hereinare implemented as a software routine, hardware circuit, firmware, or acombination thereof.

Embodiments of the disclosure can be represented as a computer programproduct stored in a machine-readable medium (also referred to as acomputer-readable medium, a processor-readable medium, or a computerusable medium having a computer-readable program code embodied therein).The machine-readable medium can be any suitable tangible, non-transitorymedium, including magnetic, optical, or electrical storage mediumincluding a diskette, compact disk read only memory (CD-ROM), memorydevice (volatile or non-volatile), or similar storage mechanism. Themachine-readable medium can contain various sets of instructions, codesequences, configuration information, or other data, which, whenexecuted, cause a processor to perform steps in a method according to anembodiment of the disclosure. Those of ordinary skill in the art willappreciate that other instructions and operations necessary to implementthe described implementations can also be stored on the machine-readablemedium. The instructions stored on the machine-readable medium can beexecuted by a processor or other suitable processing device, and caninterface with circuitry to perform the described tasks.

The above-described embodiments are intended to be examples only.Alterations, modifications and variations can be effected to theparticular embodiments by those of skill in the art. The scope of theclaims should not be limited by the particular embodiments set forthherein, but should be construed in a manner consistent with thespecification as a whole.

The invention claimed is:
 1. A method comprising: receiving, by a userequipment (UE) from a base station (BS), a high-level signalingindicating a resource allocation that allocates, to the UE, firstresource(s) for an initial grant free uplink transmission of a datapacket and second resource(s) for grant free uplink retransmission(s) ofthe data packet, the first resource(s) and the second resource(s) beingwithin the same partition of an uplink channel, wherein the high-levelsignaling further includes an assignment indicating a number of grantfree retransmissions for the data packet, the assignment being specificto the UE; and transmitting, by the UE, the initial grant free uplinktransmission of the data packet and the grant free uplinkretransmission(s) of the data packet, the initial grant free uplinktransmission being transmitted via the first resource(s), and the grantfree uplink retransmission(s) of the data packet being transmitted viathe second resource(s) based on the resource allocation indicated by thehigh-level signaling and the number of grant free retransmissionsindicated by the assignment in the high-level signaling; and whereintransmitting the initial grant free uplink transmission of the datapacket and the grant free uplink retransmission(s) of the data packetcomprises: transmitting, by the UE, the initial grant free uplinktransmission of the data packet and the grant free uplinkretransmission(s) of the data packet without determining whether theinitial grant free uplink transmission has been successfullytransmitted.
 2. The method of claim 1, wherein the first resource(s) arelocated in a frequency partition, the first resource(s) being timefrequency resources dedicated to grant-free transmissions.
 3. The methodof claim 1, wherein the grant free uplink retransmission(s) of the datapacket are transmitted using a different modulation and coding scheme(MCS) than the initial grant free uplink transmission of the datapacket.
 4. The method of claim 1, wherein the resource allocationallocates different frequency resources to the initial grant free uplinktransmission of the data packet than to the grant free uplinkretransmission(s) of the data packet.
 5. A method comprising:transmitting, from a base station (BS) to a user equipment (UE), ahigh-level signaling indicating a resource allocation that allocates, tothe UE, first resource(s) for an initial grant free uplink transmissionof a data packet and second resource(s) for grant free uplinkretransmission(s) of the data packet, the first resource(s) and thesecond resource(s) being within the same partition of an uplink channel,wherein the high-level signaling further includes an assignmentindicating a number of grant free retransmissions for the data packet,the assignment being specific to the UE; and receiving, by the BS, theinitial grant free uplink transmission of the data packet and the grantfree uplink retransmission(s) of the data packet, the initial grant freeuplink transmission being received via the first resource(s) and thegrant free uplink retransmission(s) of the data packet being receivedvia the second resource(s) based on the resource allocation indicated bythe high-level signaling and the number of grant free retransmissionsindicated by the assignment in the high-level signaling, wherein thegrant free uplink retransmission(s) of the data packet are from the UEwithout the UE determining whether the initial grant free uplinktransmission has been successfully transmitted.
 6. The method of claim5, wherein the first resource(s) are located in a frequency partition,the first resource(s) being time frequency resources dedicated togrant-free transmissions.
 7. The method of claim 5, wherein each of thegrant free uplink retransmission(s) of the data packet are transmittedusing a different modulation and coding scheme (MCS) than the initialgrant free uplink transmission of the data packet.
 8. The method ofclaim 5, wherein the resource allocation allocates different frequencyresources to the initial grant free uplink transmission of the datapacket than to the grant free uplink retransmission(s) of the datapacket.
 9. A user equipment (UE) comprising: a processor; and anon-transitory computer readable storage medium storing programming forexecution by the processor, the programming including instructions thatcause the UE to: receive, from a base station (BS), a high-levelsignaling indicating a resource allocation that allocates, to the UE,first resource(s) for an initial grant free uplink transmission of adata packet and second resource(s) for grant free uplinkretransmission(s) of the data packet, the first resource(s) and thesecond resource(s) being within the same partition of an uplink channel,wherein the high-level signaling further includes assignment indicatinga number of grant free retransmissions for the data packet, theassignment being specific to the UE; and transmit the initial grant freeuplink transmission of the data packet and the grant free uplinkretransmission(s) of the data packet, the initial grant free uplinktransmission being transmitted via the first resource(s), and the grantfree uplink retransmission(s) of the data packet being transmitted viathe second resource(s) based on the resource allocation indicated by thehigh-level signaling and the number of grant free retransmissionsindicated by the assignment in the high-level signaling; and wherein theinstructions further cause the UE to: transmit the initial grant freeuplink transmission of the data packet and the grant free uplinkretransmission(s) of the data packet without determining whether theinitial grant free uplink transmission has been successfullytransmitted.
 10. The UE of claim 9, wherein the first resource(s) arelocated in a frequency partition, the first resource(s) being timefrequency resources dedicated to grant-free transmissions.
 11. The UE ofclaim 9, wherein the grant free uplink retransmission(s) of the datapacket are transmitted using a different modulation and coding scheme(MCS) than the initial grant free uplink transmission of the datapacket.
 12. The UE of claim 9, wherein the resource allocation allocatesdifferent frequency resources to the initial grant free uplinktransmission of the data packet than to the grant free uplinkretransmission(s) of the data packet.
 13. A base station comprising: aprocessor; and a non-transitory computer readable storage medium storingprogramming for execution by the processor, the programming includinginstructions that cause the base station to: transmit, to a userequipment (UE), a high-level signaling indicating a resource allocationthat allocates, to the UE, first resource(s) for an initial grant freeuplink transmission of a data packet and second resource(s) for grantfree uplink retransmission(s) of the data packet, the first resource(s)and the second resource(s) being within the same partition of an uplinkchannel, wherein the high-level signaling further includes an assignmentindicating a number of grant free retransmissions for the data packet,the assignment being specific to the UE; and receive the initial grantfree uplink transmission of the data packet and the grant free uplinkretransmission(s) of the data packet, the initial grant free uplinktransmission being received via the first resource(s), and the grantfree uplink retransmission(s) of the data packet via being received thesecond resource(s) based on the resource allocation indicated by thehigh-level signaling and the number of grant free retransmissionsindicated by the assignment in the high-level signaling, wherein thegrant free uplink retransmission(s) of the data packet are from the UEwithout the UE determining whether the initial grant free uplinktransmission has been successfully transmitted.
 14. The base station ofclaim 13, wherein the first resource(s) are located in a frequencypartition, the first resource(s) being time frequency resourcesdedicated to grant-free transmissions.
 15. The base station of claim 13,wherein each of the grant free uplink retransmission(s) of the datapacket are transmitted using a different modulation and coding scheme(MCS) than the initial grant free uplink transmission of the datapacket.
 16. The base station of claim 13, wherein the resourceallocation allocates different frequency resources to the initial grantfree uplink transmission of the data packet than to the grant freeuplink retransmission(s) of the data packet.